The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In the state of the art, the technical problem raised by the formation of ice on the air intake of an aircraft engine nacelle has already been solved. The technical problem is raised by the presence of a leading edge of the aircraft placed in a humid air flow path so that the pressure produced by the penetration of the leading edge in the air flow path induces the ice deposition which gradually clutters the leading edge.
A solution has in particular been described for the de-icing of a leading edge whether it is an aircraft wing or tail unit edge or a nacelle air intake lip, but whose interior is lined with a material or cellular structure for reducing acoustic noise in the document FR-A-2,912,781. In this document, a coating for the acoustic processing added at a surface of an aircraft is described, in particular at a leading edge such as an air intake of an aircraft nacelle. The coating includes an acoustically resistive layer, at least one cellular structure and a reflective layer. The cellular structure includes a plurality of ducts opening, on the one hand at a first imaginary surface, and on the other hand, at a second imaginary surface.
In this state of the art, the cellular structure comprises cutouts or orifices arranged at side walls of some ducts allowing to communicate adjacent ducts so as to create a network of communicating ducts insulating at least one duct or a group of non-communicating ducts, at least one of the communicating ducts being connected to at least one hot gas supply.
Forming cutouts and orifices in the cell walls is difficult. It is expensive to machine and it does not allow large-sized cellular structures. Furthermore, the hot air distribution in the cellular structure is not optimal which leads to increases in the hot air distribution pressure and is not always feasible.
In another known structure (see FR-A-2,981,049), piercing cutouts or orifices in the cell walls to constitute ducts is replaced by grooving of the face of the acoustic absorbent material intended to be placed on the inner surface of the skin of the nacelle which faces, at the air intake of the nacelle and inwardly of the nacelle facing the fan blades in the case of a turbojet engine. This skin is itself pierced with perforations or micro-perforations which are in fluid communication with the thus constituted grooves. In this state of the art, an annular shaped piccolo tube is supplied with hot air by a duct coming from a hot air generator or source, when a de-icing operation is controlled. The hot air is diffused through the piccolo tube, itself perforated, and enters in the grooves of the inner face of the cellular structure, it can then be diffused through the perforations or micro-perforations of the inner skin of the air intake of the nacelle. The de-icing effect is thus produced on the air intake of the nacelle.
In this other state of the art, the grooving is an improvement for the work of the cellular structure. But it is not particularly adapted to the primary distribution of hot air through the piccolo tube.